Technical Field
Embodiments of the present invention generally relate to memory devices. More particularly, embodiments relate to throttling memory in a computer system.
Discussion
While recent trends in the computer industry toward smaller computing platforms and greater functionality have been desirable to consumers, these trends have presented a number of challenges to computer system designers as well as manufacturers. For example, designing notebook personal computers (PCs), personal digital assistants (PDAs) and wireless “smart” phones can be quite difficult due to the small form factor of these systems and their susceptibility to component overheating. In particular, excessive temperatures can cause processors, memory devices and other components to operate at a less than optimum performance level. In some cases, overheating can cause device failure. Overheating can also cause safety concerns with regard to the surface temperature of the platform enclosure. In addition, the applications being designed for computer systems continue to demand an increasing amount of power, which has a direct effect on temperature. For example, 3D gaming applications and “always-on” wireless features are just a sampling of the types of relatively high power applications available to consumers. When such applications are incorporated into small form factor computer systems, thermal concerns increase even more.
To better manage the above-described concerns, many computer designers establish a thermal design power (TDP) limit for a given platform, where the TDP essentially defines a power threshold that the platform should operate below in order to minimize overheating-related performance losses and safety concerns. In particular, it has been determined that accesses to memory units such as system memory can contribute significantly to the power consumption of the overall system. To address this problem, some solutions involve incorporating a temperature sensor into a memory controller hub (MCH), where the MCH controls accesses to the memory unit over a memory bus. If the temperature of the MCH exceeds a pre-set value, the memory unit is “throttled” by reducing memory access traffic to the memory unit.
While the above-described approach has been suitable under certain circumstances, a number of difficulties remain. For example, the temperature measured within the MCH does not reflect the actual internal temperature of the memory unit. As a result, correlating the measured temperature to the actual temperature can be difficult and may result in inaccuracies. Furthermore, to offset the risk of inaccurate temperature measurement, many designs involve overly conservative temperature limits and are therefore associated with significant performance losses. Another difficulty with the conventional approach relates to response time. In particular, some memory devices such as synchronous dynamic random access memory (SDRAM) devices have relatively high current surge transients that may require immediate shutdown in cases of overheating. The relatively long response time of the conventional approach, however, may not be able to detect the overheating in time because the temperature is measured at the MCH.